带卸载的下行多天线HetNets干扰置零分析与优化
Analysis and Optimization of Interference Nulling in Downlink Multi-Antenna HetNets with Offloading
摘要：
具有卸载的异构网络（HetNet）被认为是满足未来无线业务的高数据率需求的有效方式。然而，卸载的用户遭受强烈的层间干扰，这降低了卸载的益处，并且是系统性能的主要限制因素之一。在本文中，我们研究了使用干扰置零（IN）波束成形方案，以提高系统性能，通过仔细管理层间干扰的卸载用户在下行链路两层HetNet与多天线基站。利用随机几何的工具，我们推导出一个易于处理的表达率覆盖概率的IN计划。然后，我们优化设计参数，即，可以用于IN的自由度，以最大化速率覆盖概率。具体地说，在渐进的情况下，速率阈值是小的，通过研究的速率覆盖概率的顺序行为，我们的最佳设计参数的特征。对于一般情况下，我们展示了最优设计参数的一些性质。最后，通过数值模拟，我们表明IN方案可以优于简单的卸载方案没有干扰管理和几乎空白的子帧方案在3GPP LTE中，特别是在大天线制度。
英文摘要：
Heterogeneous networks (HetNets) with offloading is considered as an effective way to meet the high data rate demand of future wireless service. However, the offloaded users suffer from strong inter-tier interference, which reduces the benefits of offloading and is one of the main limiting factors of the system performance. In this paper, we investigate the use of an interference nulling (IN) beamforming scheme to improve the system performance by carefully managing the inter-tier interference to the offloaded users in downlink two-tier HetNets with multi-antenna base stations. Utilizing tools from stochastic geometry, we derive a tractable expression for the rate coverage probability of the IN scheme. Then, we optimize the design parameter, i.e., the degrees of freedom that can be used for IN, to maximize the rate coverage probability. Specifically, in the asymptotic scenario where the rate threshold is small, by studying the order behavior of the rate coverage probability, we characterize the optimal design parameter. For the general scenario, we show some properties of the optimal design parameter. Finally, by numerical simulations, we show the IN scheme can outperform both the simple offloading scheme without interference management and the almost blank subframes scheme in 3GPP LTE, especially in large antenna regime.
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